The present invention relates generally to a cylinder lock and then particularly to a cylinder lock-key combination with an eccentrically placed key.
Ever greater demands are placed on present day lock devices, thereamong cylinder locks, with regard to safety and also with regard to compact lock designs. One way of enhancing safety is to increase the number of code surfaces, which in the case of a pin tumbler cylinder implies an increase in the number of pins. However, an increase of the nature involved makes it difficult to provide a compact lock construction.
U.S. patent document U.S. Pat. No. 3,348,392 describes a method of systematisation that requires a large number of code surfaces. This system is based on leaving a few code pin channels empty, instead of utilising all available channels. This results in a systematisation in which the use of intermediate pin tumblers is avoided. In order to achieve a large number of code surfaces, the document proposes the use of a key that has a circular cross-section in the key bit, which is placed centrally in an opening in the cylinder plug intended to this end. One problem with this solution resides in the difficulty in producing a compact lock of small diameter.
The Austran Patent Specification 368 235 describes a cylinder lock that includes code-guided, enable a block device, such as a side bar, to leave an opening provided in the cylinder housing, in a correct code position. The key is comprised of a relatively thick material and code surfaces are disposed at the junction between the side surface and the upper surface of the key bit. Moreover, the waisted pins extend obliquely in the lock plug. The illustrated solution is therefore space demanding and, consequently, unsuitable for small locks.
One object of the present invention is to provide a highly secure cylinder lock-key combination which, at the same time, enables the lock cylinder or plug to be given a compact construction.
The invention is based on the realisation that a secure and, at the same time, a compact cylinder lock construction can be achieved by a combination of an eccentrically placed key and code pin channels disposed in the bottom of a recess in the barrel surface of the cylinder plug.
Accordingly, an inventive cylinder lock-key combination has the features defined in the accompanying claim 1.
Other preferred embodiments are apparent from the accompanying dependent claims.
An inventive cylinder lock-key combination provides a high degree of security as a result of the large number of code pins, which also makes possible the inventive systematisation principle. Because the key opening is placed on the periphery of the cylinder plug and the pin tumblers co-act with code surfaces disposed on the side surface of the key bit, the large number of cylinder pins and at the same time, the cylinder plug can be made short and given a small diameter.